Research And Design Of MIMO Antenna For 5G Wearable Terminals

With the comprehensive development of 5G communication and the intelligent application of wearable devices in recent years,wearable terminals have urgent needs for high speed and high throughput,and need to have multiple input and multiple output characteristics in important communication frequency bands.Wearable devices such as smart watches and smart eyewears,whose area that can be used for designing antennas is limited.Therefore,the multi-port arrangement design of MIMO antenna arrays and the decoupling between elements face challenges.Electromagnetic radiation safety should also be considered,as a wearable terminal device close to the human body.Aiming at the problems of multi-port high isolation,conformal design and radiation safety of MIMO antennas in wearable terminal devices,this thesis designs MIMO antennas suitable for watch terminals and glasses terminals,and proposes a SAR reduction plan suitable for MIMO array multi-antennas.First of all,the decoupling of MIMO antennas for watch terminals is analyzed.Two highisolation MIMO antenna pairs suitable for 5G watch terminals are designed using polarization orthogonal technology.The first antenna pair can cover the 3.4GHz-3.6GHz frequency band,and the isolation between the two ports is above 15 d B.Then,a 4×4 MIMO antenna array is designed by combining the designed antenna pairs.Finally,the isolation between any port reaches more than 10 d B,the ECC is less than 0.05.The second antenna pair adopts the structure multiplexing technology,which can cover the 4.8GHz-5GHz frequency band,and the isolation between the two ports is above 15 d B.Then,a 4×4 MIMO antenna array is designed by combining the designed antenna pairs.Finally,the isolation between any port reaches more than 15 d B,and the ECC is less than 0.01.Both MIMO antennas feature small size,high isolation,good bandwidth coverage,and low envelope correlation coefficients.Secondly,the decoupling of MIMO antennas for eyewear terminals is analyzed.By using the characteristic mode analysis,the excitation of multiple orthogonal modes in the same frequency band is realized,and a high-isolation MIMO antenna group suitable for 5G eyewear terminal is designed.The three elements of the MIMO antenna group can cover the3.4GHz-3.6GHz frequency band,and achieve a three-port isolation higher than 10 d B on the basis of the common radiator.Then,a 6×6 MIMO antenna array is designed,the isolation between any port reaches more than 10 d B,the ECC is less than 0.1,and efficiencys of the MIMO antenna array are higher than 55%.The eyewear MIMO array antenna can better conform to the glasses frame,and has the performances of high isolation,good bandwidth coverage,and low envelope correlation coefficient.Finally,the radiation safety of the antenna for the watch terminal is analyzed,and a watch antenna that can work in the 4.8GHz-5GHz of 5G communication high frequency band is designed.A SAR reduced scheme is proposed based on the characteristic mode theory,and the SAR value is reduced by 34%.Then a 2×2 MIMO antenna array is designed to verify the applicability of the above-mentioned SAR reduction scheme in MIMO arrays.The SAR peak value of the dual-antenna array under the premise of 0°-360° phase difference traversal is reduced by more than 30%,and the antenna efficiency drop is kept within 1d B.The SAR reduction scheme has good application value in the field of wearable terminal equipment and MIMO antenna design.